Riverside County supervisors Tuesday unanimously green-lighted the writing of a measure that would mandate all pit bulls and pit bull-mix dogs kept in unincorporated county communities be sterilized.

The move, which could lead to the adoption of a mandatory spay-neuter law in a few weeks, followed the testimony of 11 public speakers who were nearly evenly split on the matter.

Sarah Kosinski-Cope, founder of Change of Heart Pit Bull Rescue in Norco, told supervisors she supports sterilization but not a policy that singles out a specific breed. And she urged the county to instead provide low-cost and free spay-neuter clinics for pit bull owners to assist people who cannot afford to sterilize their pets.

Aurora Chavez of Riverside was more blunt in her opposition.

“You’re genociding a whole breed of animals,” she said.

Chavez said she has a sweet-tempered female pit bull mix named Bella, and dogs of that particular breed are vicious only if their owners train them to be that way.

But the problem with the breed, said Beaumont Councilwoman Brenda Knight, is that pit bulls that are vicious are significantly more dangerous than aggressive dogs of other breeds.

“They bite like sharks,” said Knight, who backed the proposal. “They rip and tear and shred. That’s why they are in the news.”

Willa Bagwell, executive director for Animal Friends of the Valleys in Wildomar, added, “The shelters are full of pit bulls that can’t be adopted.”

That is certainly the case with county-run shelters, where 1 in 5 dogs are pit bulls, said Robert Miller, director of the Riverside County Department of Animal Services.

Allan Drusys, the county’s chief veterinarian, said after the meeting that 40 percent of all dogs are euthanized because homes aren’t found for them and about 80 percent of pit bull strays are put down.

Miller sought to ease anxiety about the pending measure, saying the county was not proposing to wipe out pit bulls or to go door to door looking for violators.

But because dogs of that breed have caused much damage recently, there is a need to control their fertility, he said.

He cited recent attacks on elderly women in Jurupa Valley and Hemet, and a 10-year-old boy in the Beaumont area.

“Pit bulls were bred to be champions,” Miller said. “And they were bred to be champions in one type of work: fighting.”

At the same time, Miller said the county anticipates exempting certain owners and operations from mandatory sterilization, such as those who train them to be service dogs.

Ricardo Bengochea of San Jacinto told the board he has trained 25 pit bulls to be service dogs for disabled veterans and others.

“They are not just stereotypes,” Bengochea said.

As for the board, Supervisor John Tavaglione said he asked for the measure in the wake of the recent attacks. And Supervisor Marion Ashley said it was “badly needed.”

But Supervisor Kevin Jeffries of Lakeland Village cautioned that a county measure would barely scratch the surface of controlling attacks, given it would apply only in unincorporated areas, unless cities follow suit.

“It’s an immediate setup for failure,” Jeffries said.

Ashley said the county should develop a model ordinance for the cities, as it did in the area of water conservation several years ago.

He noted that the water measure was widely adopted by municipalities.

“They’re looking for leadership,” Ashley said. “It’s up to us to lead. And then we’re going to have to go sell it.’”